Help! which di2 specs?


New Member
Oct 18, 2020
Hi Everyone, I'm new to the forum and was hoping you guys can help me out. Looking for expert advice here :)

I have an older (but awesome) 2012 Tarmac Pro SL4 Mid-Compact Ui2 (first gen) bike which I want to upgrade to Di2 (among other things to save weight, battery life and climbing ease). Treating myself to a well deserved Bday gift here. Doing the research I realized there are way too many questions I am not sure about before pulling the trigger in such a pricey upgrade.

My ride: if you google, first link should be it "2012 Specialized Tarmac SL4 Pro Ui2 mid-compact" (wouldn't allow me to past the link)

1. Battery mount > can my ride use the internal seatpost set up? (currently have the 1st gen external water cage)
2. Junction Box A > In frame? Under stem external? in-handler bar internal? (can my ride allow internal?)
3. Junction Box B: not sure which one I need. can my ride fit the EW-WU111 wireless?
4. Wires: which dimensions! EW-JC130, EWSD50
5. Cranks & Cassette: looking for a 10-34T and 34T small crank up-front (yeah I am that bad going up!). Should I get the ultegra 10-34T (Dura Ace seems to only go to 30T) with a long long shaft RD? Crankset: Can I get the 52-36 and switch the small crank for 34T? (would a long GS RD deal with chain tension?) or should I stick to the 50-34 crankset? Would you advice any different if thinking on getting a Power Meter too?
6. R9100 Calipers > Standard or Direct Mount? (not sure the difference)

Thanks a bunch! Sorry for the long post but I am sure there are people out there who can answer these in a heart beat!